1. Field of the Invention
The present invention relates to an imaging apparatus, such as a digital still camera and a video camera. In particular, the present invention relates to a lens barrel, which includes an opening/closing barrier member provided on a front surface of a photographic optical system to protect the photographic optical system, and an imaging apparatus.
2. Description of the Related Art
A conventional camera system having a solid-state image sensor, such as a digital still camera and a video camera, shoots a still image and a moving image by using one or more image sensors and records the taken image on a recording unit, such as a memory.
The above-described conventional camera system can use a part of an imaging area of the image sensor for a function other than an image shooting function.
Japanese Patent Application Laid-Open No. 2000-292686 discusses a method for executing a pupil division function by using a light receiving portion (a part of the image sensor) of pixels, which is divided into two. The method discussed in Japanese Patent Application Laid-Open No. 2000-292686 uses the pixel as a focus detection pixel and arranges the focus detection pixels between imaging pixels at a predetermined interval. Thus, the method implements phase difference focus detection.
On the other hand, a defect may occur on a pixel constituting an image sensor during manufacture of the image sensor. The defect includes a white flaw, which may cause the level of an output signal of the defective pixel to increase, a black spot pixel, which may cause the level of an output signal of the defective pixel to decrease, and poor linearity of an output signal.
If a pixel set in a focus detection area has the above-described defect, an error may occur in a result of focus detection.
In order to address the above-described problem, Japanese Patent Application Laid-Open No. 2001-177756 discusses a method for reducing an effect from the defective pixel by moving the entire focus detection area if a pixel set in a focus detection area includes a defect.
However, in a camera discussed in Japanese Patent Application Laid-Open No. 2000-292686, if a pixel set in the focus detection area includes a defect, it is necessary to discard the defective image sensor in order to prevent an error that may occur in the result of focus detection.
An image sensor is a relatively expensive component among those of a camera system. Accordingly, if a pixel set in the focus detection area includes a defect and if the image sensor including the defective pixel is discarded, the cost of manufacture of the imaging apparatus and the camera system may increase.
In addition, a camera discussed in Japanese Patent Application Laid-Open No. 2001-177756 moves the focus detection area to an area including no defective pixel. Accordingly, the camera discussed there may focus on an object different from an object of an image that a user of the camera desires to capture.